On Apr 5, 2007, at 12:02 PM, Chuck Hill wrote:
public WOActionResults postsAction() {
WOComponent nextPage = pageWithName("TopicPosts");
Number topicID = request().numericFormValueForKey("topicID",
new NSNumberFormatter());
EOEnterpriseObject topic =
EOUtilities.objectWithPrimaryKeyValue(WOApplication.application
().sharedEditingContext(), "Topic", topicID);
That rather looks like an abuse of sharedEditingContext().
That it does! According to the EOSharedEditingContext docs, only 4
EOSharedEditingContext methods that make changes to the shared
editing context are thread-safe. We don't know whether
EOUtilities.objectWithPrimaryKeyValue() uses one of these thread-safe
methods. If it doesn't, the shared editing context must be locked
prior to its use, something that can be difficult to do correctly.
Instead, fetch all shared objects that an app instance will need in
the Application constructor using one of the thread-safe methods.
Then access these shared objects by sending the shared editing
context either an objectsByEntityName() or
objectsByEntityNameAndFetchSpecificationName() message, getting the
array of objects for the particular entity (e.g., Topic) from the
returned dictionaries, and then filtering this array, if necessary,
to get the object(s) desired.
Also, exposing the Topic primary key, normally a meaningless
integer, and then using it to get a Topic object isn't the pattern
usually used for the Enterprise Objects Framework (EOF). Instead,
an attribute whose value is unique and meaningful to humans is a
better choice for accessing an object. E.g., topicName, if such
attribute exists.
Number topicID = request().numericFormValueForKey("topicID",
new NSNumberFormatter());
EOEnterpriseObject topic =
EOUtilities.objectWithPrimaryKeyValue(WOApplication.application
().sharedEditingContext(), "Topic", topicID);
EOEnterpriseObject topic;
String topicName = request().formValueForKey("topicName");
if (topicName != null) {
NSArray topics = WOApplication.application
().sharedEditingContext().objectsByEntityName().objectForKey("Topic");
EOQualifier qual = new EOKeyValueQualifier("topicName",
EOQualifier.QualifierOperatorLike, topicName);
topic = (EOEnterpriseObject)
EOQualifier.filteredArrayWithQualifier(topics, qual).lastObject();
}
else {
topic = null;
}
if (topic == null) {
// Deal with no Topic object.
}
While this may appear more verbose,
EOUtilities.objectWithPrimaryKeyValue() can throw 3 exceptions, so it
should be in a "try" block with "catch" blocks dealing at least one
of these exceptions. Once you've done all
Number index = request().numericFormValueForKey
("displayBatchIndex", new NSNumberFormatter());
// set variables
nextPage.takeValueForKeyPath(topic,
"postsDisplayGroup.masterObject");
if (index != null) nextPage.takeValueForKeyPath(index,
"postsDisplayGroup.currentBatchIndex");
return nextPage;
Also, as others have warned, using KVC to set and get values
increases the probability of run-time exceptions should you mistype a
key or key path. Such errors won't be caught by the compiler.
Instead, send actual Java messages. Any mistyping of these messages
will be caught at compile time rather than at run time which is much-
preferred :-)
WODisplayGroup postsDG = nextPage.postsDisplayGroup();
postsDG.setMasterObject(topic);
if (index != null) postsDG.setCurrentBatchIndex(index);
Aloha,
Art
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